Fix support for vector units with Zvfh #1003

Job	Run time
riscv-arch-test	0s
emulator (DefaultSmallConfig)	13m 11s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.DefaultC...	21m 22s
emulator (DualBankConfig)	13m 19s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.DefaultR...	19m 54s
riscv-tests (DefaultConfig)	13m 41s
emulator (DualChannelConfig)	13m 31s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.WithDebu...	18m 4s
riscv-tests (DefaultBufferlessConfig)	13m 40s
emulator (DualChannelDualBankConfig)	13m 29s
jtag-dtm-test (freechips.rocketchip.system.WithJtagDTMSystem_freechips.rocketchip.system.WithDebu...	17m 8s
riscv-tests (DefaultRV32Config)	13m 40s
emulator (RoccExampleConfig)	13m 32s
emulator (Edge128BitConfig)	13m 28s
riscv-tests (TinyConfig)	13m 41s
riscv-tests (DefaultFP16Config)	13m 23s
emulator (Edge32BitConfig)	13m 27s
emulator (QuadChannelBenchmarkConfig)	13m 20s
emulator (EightChannelConfig)	13m 39s
emulator (DualCoreConfig)	13m 21s
emulator (MemPortOnlyConfig)	12m 46s
emulator (MMIOPortOnlyConfig)	12m 51s
emulator (CloneTileConfig)	14m 52s
emulator (HypervisorConfig)	12m 56s
	5h 32m 15s

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